Charles e



(No Model.)

0'. E; SCRIBNER. SIGNALING SYSTEM FOR TELEPHONE TRUNK LINES. No. 513,587.

. .Patented- Jam 30, 18.94.

WITNESSES INVENTEIR I fly. v rneys.

we NAHONAL umurmAM-lma COMPANY, wuummon. n. c.

UNTTEE STATES PATENT FFKQEQ CHARLES E. SCRIBN ER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERN ELECTRIC COMPANY, OF SAME PLACE.

SIGNALING SYSTEM FOR TELEPHONE TRUNK-LINES.

SPECIFICATION forming part of Letters Patent No. 513,537, dated January 30, 1894. Application filed June 16, 1893. Serial No. 477,358- (No model.)

To wZZ whom it may concern:

Be it known that I, CHARLES E. SGRIBNE a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Signaling Systems for Trunk- Lines of Telephone-Exchanges, (Case No. 326,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a part of this specification.

My invention relates to apparatus for signaling between the different operators in a telephone exchange system who may be engaged in establishing connection between two different lines through the medium of a trunk or transfer line; its objectis to provide means whereby each operator will be automatically notified of the acts performed by the other operator in establishing such connection.

My invention is particularly applicable in central offices in which the signal receiving annunciators upon different lines are distributed upon different answering boards and the spring-jacks or connection sockets are arranged together upon a large switchboard, the call signals being received by an answering operator, and the connection between the calling line and the line called being completed by a switchman at the switching section, in accordance with the .orders of the answering operator. In such systems trunk lines or transfer circuits are provided, extending from the answeringoperator to the switchman; the answering operator makes connecnection between the callingline and the trunk line by'means of suitable appliances at her answering board, while the switchman establishes connection from the other terminal of the trunk line to a springjack of the line with which connection is ordered, thus looping the two lines into a continuous circuit including the trunk line and the connecting appliances at the answering board.

The object of my invention is, more specifically, to provide circuits and apparatus of simple and efficient character in connection with these trunk lines, whereby the answering operator may be made aware of the steps taken by the switchman in establishing an ordered connection, and, further, whereby the act of the removal of the connection at the answering board will automatically signify to the switchman that the connection upon the switchboard is to be removed.

Speaking in a general manner,l provide in my invention an independent local circuit extending between the terminal stations of the trunk line, normally open at the answering board and normally closed at the switchmans board, including at each station a sig nal instrument adapted to give a visible or other indication and a source of current, in combination with means for automatically closing the local circuit at the answering board by the establishment of the connection with the terminal of the trunk line thereat, and a key at the switchmans section for connecting the switchmans telephone with the trunk line, which key also controls the continuity of the signaling circuit and the connections of the switchmans signal indicator so that whenever the signaling circuit is opened at the switchmans station, a local circuit is closed through the switchmans indicator. For this indicator I preferably employ a device which gives an indication only when no current traverses it. Thus the switch mans indicator is only operated or displayed upon the breaking of the signaling current at the answering station, while the indicators at the answering board are controlled by the circuit closers at both stations.

In practice one trunk line is usually connected With springjacks or connection sockets upon several different answering boards, i order that any of the several answering opa ators may utilize the trunk line in extendi e a circuit to the switchmans board. b

In my invention Iextend the signaling i cuit to each of the answering boardswh iis a connection socket of the trunk lin d provide a signaling instrument and mean for closing the local circuit in connection with each such jack. All the indicators of one signaling circuit, upon the different answering boards, are simultaneously actuated or caused to respond when the local circuit is closed, so that they constitute signals upon all the answering boards to indicate that the corresponding trunk line is in use.

I have illustrated my invention in the aaswering operator to connect with the line.

companying drawing, and will describe it fully in connection therewith.

In the drawing two substations-are represented as connected by line wires with springjacks or terminal sockets upon a switchboard, and with annunciators upon two answering boards, the different annunciators being located upon the different answering boards. An answering springjack is provided for each line near its annunciator to permit the at;- trunk line is shown extending from the answering boards, being connected with one springjack upon each of the answering boards, to the switchmans section, and my improved signaling system is shown in combination with the trunk line. The usual connecting appliances are-represented at one of the answeringboards as in the position of establishing-connection between one of the lines and the trunk line. The trunk line is connected at the switchboard with the remainingline, whereby the two substations are connectedtogether in a continuous circuit.

Considering-the system in greater detail, I will trace the various circuits and describe the operations involved in establishing connection-between the two substations indicatingparticularly the operation and utility of my'invention.

Substation 1, for example, is connected with thecentral station by means of a line circuit a a; the different sides of this circuit are connected with the thimble b and line spring b, respectively, of a springjack c which is located upon the switchboard cl at the central office. From the springjack c the circuit is continued to an annunciator 6 upon an answering board f. An answering springjack g is also provided upon this answering board having its-thimble and line spring connected with'the sides a a, respectively, in a manner similar to the springjack c. The springjacks are provided with contact an vils against which the'line-springs normally rest, but from which they are separated when a connecting plug is inserted into the spring-jack. Thus when connection is made with either springjack, the remainder of the circuit including the annunciator is disconnected from the portion of theline extending to the substation. The substation 2 is similarly connected by line wires a a with a springjack 0 upon the switchboard d, and also with an annunciator e and answering jack g upon an answering board f. The connecting appliances provided at theanswering board f are shown in full, but the corre'spondingapparatus at board f is not shown. Theseconnecting appliances are of well known character. The apparatuscomprises a pair of loop plugs h h connected together by conductors 11 i so that by inserting the two plugs into two springjacks, the lines connected with the springjacks are looped into a continuous metallic circuit. Included in the conductors 2' 1." are two calling keys 70', each of which is adapted, when furnished for the operator, connected with a listening key it, by depressing which the telephone set is connected with the plug circuit and theoperator is placed in telephonic communication with the substations. A grounded battery 0 is connected at its free pole with the conductor 4] for testing purposes, a retardation coil being included in the branch between the battery and the conductor of the plug circuit to prevent the escape of telephonic current to earth.

The trunk ortransfer circuit 10 p is connected with springjacks q and q, one upon each of the answering boards ff. These springjacks are not provided with separable switch contacts, but consist simply of flexible line springs r and thimbles r adapted to make contact with the corresponding, portions of the loop plug h. From the answering boards the trunk circuit extends to the,

In my invention two additional local springs r r are provided upon the springjacks q q of the trunk circuit at the answering boards. These local springs are normally separated and insulated from each other,but are adapted to be crossed together by aninsulated metallic ring r placed upon the plug h in addition to the ordinary tip and sleeve contacts thereof.

The springs r are connectedtogether and'are grounded through a battery 0. The remaining;

local springs r are connected together and with the portion 'w of the signaling circuit extending to the switchboard. Visible signals :1: 0c are included in a signaling circuit, one upon each answering board near the corresponding springjack. The signal indicator employed comprises an electromagnet y and an armature y carried upon a pivoted lever g to the upper extremity of which an indicator 3 is attached. The armature 'y" is of curved form and is arranged to swing past the pole of magnet y. A plate g is placed in position to conceal the indicator y when the latter is in its normal position, but is provided with an aperture through which the indicator appears when the magnet is ener gized, the armature being then attracted to a position opposite the polerof the magnet,

and thus swinging the indicator to itsalternate position.

The-signaling circuit w may be closed to earth at the switchboard at through the medium of a contact spring to and its contact anvil w which are brought into contact when the key it is placed in position to disconnect the telephone set t from the trunk circuit 19 p. From the contact anvil w? the circuit w is continued through a visible signalm at the switchboard d, and through a battery '0' to earth. The signaling instrument m is provided with a plate 00 whose aperture is at the opposite side from those of the instruments w 00 so that its indicator is displayed only when the magnet is not energized. The batteries 'u and o are arranged with opposite poles to earth in order that when the signaling circuit is completed, the batteries shall assist each other. Othercontact points z z are provided upon the key u normally separated but adapted to be closed together when the key is in position to connect the telephone set t with the trunk line, and when so closed,

to complete a local circuit of the battery 12'.

through the indicator {1: to earth. The normal position of the key it is that in which it connects the telephone set t with the trunk line, in readiness to receive telephonic orders over the trunk line; the contact points w Z02 are thus normally separated,opening the signaling circuit, while the contact points z z are closed together, completing the local circuit of battery o through the signaling instrument oc and retaining the indicator thereof concealed.

In the operation of the system, assume that the subscriber at stationl desires to communicate with subscriber at station 2. Rotating his signaling generator, he transmits signaling current over the line a a to the central office, where it finds circuit through springjack 0 upon the switchboard d and the answering jack 9 upon the answering board f to the annunciator 6 upon the same board, actuating the latter and notifying the attendant operator that the connection is desired. The operator then inserts a plug it of a pair into the springjack g, at the same time depressingthe plunger of her listening key m, connecting her telephone 'n with the cord circuit 2' c", whereby she is placed in telephonic communication with subscriber at station 1. Having received his order for connection with station 2, she inserts the rem aining plug it of the pair into the springjack q of the trunk line p 19' upon the answering board The connection of the cord circuit '5 t" is thus extended through the contact pieces of the plug h and the co-operatingcontacts of the springj ack q to the corresponding sides of the trunk circuit 19 p. The operator at once addressesthe switchman at switch board at and orders the trunk line 1) 1) connected with the subscribers line to station 2. The switchman thereupon inserts the terminal plug .9 of the trunk line into the springjack c of the line to station 2, completing the connection between the two lines, the circuit being continued through the plug from the conductors p p to the conductors a a of the line to station 2. The switchman then places the listening key it in its alternate position, disconnecting the telephone if from the trunk line. Circuit is now completed from earth at the answering board f through battery 0 to the spring r of springjack q, thence through the ring r to spring r from which it finds circuit through the signal indicators and as and the signal line w to the switchboard (I; there the circuit is continued through the contact points w w and the indicator m and battery o to earth. The indicators m and as are now caused to display their signals. The operation of indicator w signifies to the operator at answering board f that the connection ordered has been made and that the switchman has disconnected his telephone from the trunk line. The display of indicator m upon answering board f signifies to that operator that the trunk line pp is in use and must not be disturbed. The indicator 00 remains still undisplayed since although the local circuit of battery 0' through it was opened at contacts 2 2' when the telephone was disconnected from the trunk line, the signaling circuit is now completed through the indicator and maintains the magnetization of its magnet. The operator at answering board f, having been thus assured that connection has been made between the trunk line and line to station 2, depresses the plunger of the calling key 7c, sending a call signal to station 2 to operate the bell at the station. When the subscriber at station 2 has responded, the operator disconnects her telephone m from the plug circuit 1} 2" by permitting the plunger of listening key at to rise. When the connected subscribers have finished their conversation, one of them-for example subscriber at station 1-again rotates his calling generator, transmitting a second signaling current to to the central office, where it finds circuit to the cord circuit it, and thence largely through the clearing-out an nunciator i operating the annunciator and indicating the signal for disconnection to the attendant. The answering operator then removes the plugs h and h from the springjacks. plug it from the springjack q opens the local circuit w, by removing the connection between the local springs 0 T The indicators 0c and :0 being thus de-energized return to their normal positions, concealed from view; but the de-energization of magnet y of indicatoroc permits this indicator now for the first time to display its signal. The switchman is thus apprised that the signaling circuit has been opened at the answering board by re- IIO The removal of the moving the connecting plugs to disconnect the trunk line circuit, whereby thelocal, circuit is again closed through the indicator'a: and the indicator is returned to its normal concealed position.

Having thus described my invention, I claim as new-and desire to secure by Letters Patent- 1. The combination with a trunk line extending between the terminal stations thereof provided with appliances at each station for establishing connection with the trunk line, of a signaling circuit extending between the terminal stations of the trunk line and including a signal indicator at the sending end thereofla key at the receiving end thereof adapted to control the connections of a telephone with the trunk line, and auxiliary switch contacts actuated by the said key controlling the continuityof' the signaling circuit, whereby the attendant atthe sending end'of the trunk line may be apprised of the position'of the key at the receiving station, substantially as described.

2. The. combinationwith a trunk line extending between two stations andtprovided at eachend with appliances for establishing connection with it, of a signaling-circuit extending-between the stations including a signal indicator at each of said stations, a switch at each station controlling the continuity of the signaling circuit, theswitch at the sending station being operated by the act of establishing connection with the trunkline, the switch at the receiving-station being operated in thereversenianner by the act of connecting the operators telephone with thetrunk line, substantially as described.

3. The combination withatelephone trunk line, of an independent signaling circuit extending between the terminal stations there of, contact springs included in the signaling circuit at one station adapted to close the circuit when connection is established with the trunk line, a listening key at the other station for connecting the telephonewith the trunk line, contact points controlled by the listening keyadapted to open thesignaling circuit when the telephone is connected withthe-trunk line, signal indicators in the signaling circuit at each station, and a source of electric current in the circuit, substantiallyas specified. I

4. The combination with a trunk line, of an independent signaling circuit extending between the terminal stations thereof, meansfor establishing connection with the trunk lineat either of said stations, contact points at one of said stations adapted to close the signaling circuit when connection is made with the trunk line, a listening key at the other station for connecting an opera-tors telephone with the trunk circuit, contact points controlled by the key to open the signaling 7 circuit when the telephone is connected with the trunk line, signal indicators at each staing a signal indicator at each of said stations,-.

a local branch circuit at one of said stations including a source of electric'current, and a keyat that station adapted to connect the corresponding signal indicator alternately into the signaling circuit and the local circuit, substantially as described.

6. The combination with a trunk line, of a signaling circuit extending between the terminal stations thereof normally open at one of the stations, a signal indicator at each station, means for closing the normally open signaling circuit at one of thestations, a local circuit at the other station includinga source of electric current and a key adapted to include the signal indicator alternately into the signalingcircuit and the local circuit, the said signal indicator being adapted to display its signal only when no current finds circuit through its coils,whereby the condition of the signal indicator at one stationmay be altered by alteringthe circuit connectionsat eitherstation while the condition of the signal indicator at the other-station is-altered only by changingthecircuitsat the'other terminal station of the trunk line, substantially as described.

'7. The combination with a trunk line extending between terminal stations, of a signaling circuit extending between the same stations, including a signal indicator at each station, the indicator atone of the stations being adapted to display its signal only when its magnet coils are unexcited, meansfor alteringthe continuity ofthe signalingcircuit at either station, and a local circuit adapted to be closed through the magnet coils of the indicator which displays its signal when its coils-are unexcited, when the signaling circuit is opened at the correspondingterminal station, whereby the said last mentioned indicator displays its signal only when the signaling circuit is opened at the other station, substantially as described.

8. The combination with a trunk line extending from an answering board to a switchmans board,- of a signaling circuit extending between the same stations including at the answering board an indicator adapted to display its signal when its magnet is excitedand at the switchmans board an indicator adapted to display its signal only when its magnet is not excited, contact points at theanswering board adapted to close the normally open signaling circuit thereat when connection ismade with the trunk line, a key at lIO the switchmans section for opening the sig- In witness whereof Ihereunto subscribe my naling circuit at that station, and a local cirname this 4th day of April, A. D; 1893.

cuit controlled by said key to be closed when the signal circuit is opened thereby, said local 5 circuit including the magnet coils of the indi- Witnesses:

cator at the switch mans board, substantially ELLA EDLER, as described. LUCILE RUSSELL.

CHARLES E. SORIBNER. 

